The following includes information that may be useful in understanding the present invention. It is not an admission that any of the information, publications or documents specifically or implicitly referenced herein is prior art, or essential, to the presently described or claimed inventions. All publications and patents mentioned herein are hereby incorporated herein by reference in their entirety.
Patients presenting to hospital emergency departments with breathlessness (dyspnea) as the primary complaint can have multiple causes for their condition. Breathlessness may be caused by cardiac, lung, pulmonary, non-cardiopulmonary or infectious disorders (alone or in combination) and it is important that timely and accurate diagnosis is made. Differential diagnosis strategies to address this focus on clinical workup, patient history and invasive/non-invasive test results.
With respect to the infectious diseases, pneumonia represents a significant challenge in terms of rapid diagnosis and patient numbers and there are limited biomarker options available to the clinician.
Pneumonia is a form of acute respiratory infection, which is caused by several bacterial, viral and fungal pathogens including Streptococcus pneumoniae, Haemophilus influenzae type b, Respiratory Syncytial Virus and in patients with HIV, Pneumocystis jiroveci. The resulting infection is characterised by inflammation of alveoli and an accumulation of fluid in the lungs. Symptoms of pneumonia include difficulty in breathing, increased respiratory rate, cough, fever, chills and chest pain.
Pneumonia has a high morbidity and mortality rate. Sharma S, et al., Radiological imaging in pneumonia: recent innovations. Current Opinion in Pulmonary Medicine. 2007; 13(3):159-169. It is recognized as a significant cause of morbidity and mortality worldwide, exceeding that of HIV, malaria and measles combined (UNICEF; Pneumonia: the forgotten killer of children. 2006; UNICEF/WHO, Geneva, Switzerland). Every year, pneumonia kills an estimated 1.8 million children under the age of five years, accounting for 20% of all deaths in this age group and accounting for four paediatric deaths per minute (WHO Fact Sheet No. 331, October 2011). Pneumonia incidence has been found to be closely interrelated to health inequalities with the highest prevalence in South Asia and sub-Saharan Africa.
In the United States, more than 3 million people develop pneumonia each year. Of these approximately 20% require hospitalization with an average length of stay of 5.2 days and an average admission rate of 1.17 per patient. Pneumonia accounts for 3.4% of all inpatient deaths equating to a mortality rate of 16.5 per 100,000 population (Centres for Disease Control and Prevention, Pneumonia FastStats Sheet, January 2012). In addition to the burden imposed by pneumonia in the in-patient setting, community-acquired pneumonia results in more than 10 million visits to primary care physicians and 64 million days of restricted activity per annum (Mandell L. A. Epidemiology and etiology of community-acquired Pneumonia, Infect Dis Clin North Am. 2004; 18(4):761-76).
Clinical diagnosis of Pneumonia is complicated by the fact that symptoms are not reliably predictive. In a study of 308 patients presenting to an emergency department cough was the most common symptom in patients with pneumonia (86%), but was equally common in those with other respiratory illness. Fever was absent in 31% of patients with pneumonia, abnormal findings on lung examination were found in less than 50% of the patients with pneumonia, whilst abnormal vital signs (temperature greater than 37.8 degrees C. (100 degrees F.), pulse greater than 100/min, or respirations greater than 20/min) were the best predictor, reported in 97% of patients with pneumonia. Gennis P., et al., Clinical criteria for the detection of Pneumonia in adults: guidelines for ordering chest roentgenograms in the emergency department. J Emrg Med, 1989; 7(3):263-8.
Based on current American Thoracic Society and Infectious Diseases Society of America guidelines, the gold standard for differentiation of pneumonia from acute bronchitis in patients presenting to emergency departments is the presence of lung infiltrates indicated by a chest radiograph. However chest x-ray results are an inconsistent predictor, due to variability in interpretation, and are unable to establish the causative pathogen. In addition patients presenting with community-acquired pneumonia in an out-patient setting may not get a chest x-ray due to limited accessibility and cost. Evertsen J., et al., Diagnosis and management of Pneumonia and bronchitis in outpatient primary care practices, Primary Care Resp J, 2010; 19(3):237:241.
Due to the difficulties in accurate clinical diagnosis, laboratory diagnostics are frequently utilized by physicians to assist in differentiating pneumonia from Acute Respiratory Tract Infection (ARTI), and to identify the causative pathogen to ascertain the most appropriate treatment. Laboratory diagnostics include microscopy and culture of lower respiratory tract specimens, blood cultures, detection of antigens in urine, and serology. Bartlett, J. G., Decline in microbial studies for patients with pulmonary infections, Clin. Infect. Dis. 2004; 39; 170-172. The last several years new diagnostics in the areas of antigen and nucleic acid detection have emerged, and commercial antigen detection assays are now available for several pneumonia pathogens, particularly S. pneumoniae, Legionella pneumophila, and some respiratory viruses. A new generation of immunochromatographic pneumococcal urinary antigen tests that detect the C-polysaccharide cell wall antigen have proven useful for diagnosing pneumococcal pneumonia in adults (Werno, A. M., et al., Laboratory diagnosis of invasive pneumococcal disease, Clin. Infect. Dis. 2008; 46: 926-932). Several commercial rapid-result tests, using immunochromatography, enzyme-linked immunosorbent assay, or other formats, are now available for respiratory viruses, including influenza and respiratory syncytial viruses, assisting in the differentiation of ARTI and influenza from pneumonia.
Nucleic acid detection tests (NATs), such as PCR, have also been developed for the major pneumonial pathogens, and are available as multiplex platforms. NATs are able to detect very low levels of nucleic acid from respiratory pathogens, do not depend on the viability of the target microbe, and can provide information on the presence of antibiotic resistance phenotypes. Murdoch D. R., et al., Breathing New Life into Pneumonia Diagnostics, J of Clin Micro, 2009; 47(11):3405-3408). Despite the high level of sensitivity and specificity exhibited by NATs, their commercial uptake has been limited by their cost and time required to run the test. Hindiyeh, M., et al., Evaluation of the Prodesse Hexaplex multiplex PCR assay for direct detection of seven respiratory viruses in clinical specimens, Am. J. Clin. Pathol. 2001; 116:218-224.
In sum, very often, clinical signs of pneumonia can be very elusive. At the heart of the dilemma, the question remains: “what is the fastest way to come to the correct diagnosis?” Because the faster the diagnosis is reached, the earlier the treatment begins. However, there is almost always a large lapse of time between the time of onset of symptoms and the start antibiotic therapy due to delayed diagnosis. In an attempt to achieve the rapid diagnosis of pneumonia and shortened antibiotic courses, the use of biomarkers is now being contemplated.
Physicians are becoming more and more interested in the use of biomarkers since there is no “gold standard” which is both sensitive and specific enough to help them reach the “correct” diagnosis for pneumonia. A “correct” diagnosis would be one in which the causative pathogen can be identified morphologically. However, 70% of patients with radiologically confirmed community-acquired pneumonia (CAP) do not have the causative organism identified. Some of the biomarkers which are at the offing as an adjunct in the diagnosis of pneumonia include C-reactive protein, leukocyte count, immunoglobulins, and proinflammatory cytokines. There are other biomarkers whose importance is growing, namely procalcitonin (PCT) and Triggering receptor expressed on myeloid cells-1 (TREM-1). Still other possible biomarkers being studied for their possible use in pneumonia include copeptin, cortisol, endotoxin, proadrenomedullin, amongst others. Hanssa Summah and Jie-Ming Qu, Biomarkers: A Definite Plus in Pneumonia, Mediators Inflamm. 2009: 675753 (Published online 2009 Nov. 16).
Chronic stable heart failure may easily decompensate leading to acute decompensated heart failure (ADHF). ADHF is a worsening of the symptoms, typically shortness of breath (dyspnea), edema and fatigue, in a patient with existing heart disease. It is a common and potentially serious cause of acute respiratory distress, and its most sensitive clinical sign is jugular venous distension. Brain natriuretic peptide (BNP) is a well documented and used biomarker for the diagnosis of ADHF, where elevated levels in blood relative to a control or reference level is diagnostic of this condition.
The accurate and rapid detection of acute decompensated heart failure (ADHF) or pneumonia as the cause for breathlessness is an important and large time consuming problem for emergency department doctors or general practitioners. This is because inaccurate or incomplete diagnosis coupled with resultant incorrect treatment can be fatal, due to incorrect treatment or time delays to instituting correct treatment.
There are currently no accepted or regularly used biomarkers for the detection of pneumonia. Furthermore, there is no single marker or panel of biomarkers that can diagnose whether a patient has ADHF and pneumonia. This is vitally important as the diagnosis of pneumonia is often missed in patients with diagnosed ADHF, a situation which severely compromises the effective treatment of such patients, and can prove fatal.
Human ghrelin signal peptide (GHRsp) is a 23 amino acid peptide cleaved from ghrelin (preproghrelin) (1-117) (SEQ ID NO:1). Processing of human preproghrelin is shown in FIG. 1. Human GHRsp (1-23) is shown separately in SEQ ID NO:2. U.S. patent application Ser. No. 12/922,444 (Publication No. 20110008808) describes and claims binding agents and assays for ghrelin signal peptides and fragments, including GHRsp (1-9) (SEQ ID No:3), which are reported to be useful in methods for predicting, diagnosing, assessing or monitoring acute cardiac disorders, glucose handling disorders, and diabetes in a subject.
Importantly, for example, Applicants have discovered that ghrelin signal peptide fragments are a new and reliable biomarker for pneumonia, as well as a new and reliable biomarker for acute decompensated heart failure and as a new and reliable biomarker for patients who have both pneumonia and acute decompensated heart failure.